Tuna farming

The bitter joke among fisheries scientists is that the Japanese are engaged in a dual project of turning all available knowledge and energy to the farm-rearing of bluefin tuna while simultaneously expending all available effort to catch every wild example.

This month, they succeeded in one of those aims: Hidemi Kumai and his team at Kinki University managed to raise fry born in captivity to adult size and them have them breed successfully. Because of the complexity of their life cycle, it is a considerable achievement. (Source) These are valuable fish, with the record holder having sold for $180,000 in Tokyo. The three largest fishers of Bluefin tuna are the United States, Canada and Japan.

This is good news for those who enjoy bluefin tuna sashimi, though they should probably be hoping that the rearing process can be scaled up to commercial levels. According to the US National Academy of Sciences1, present day stocks are only 20% of what existed in 1975. Some sources hold existing bluefin stocks to be just 3% of their 1960 level. Present stocks are only 12% of what the International Commission for the Conservation of Atlantic Tunas has designated as necessary to maintain the maximum sustainable yield for the resource. Within another fifty years, it is quite possible that wild bluefin tuna will no longer exist.

[1] National Academy of Sciences. National Research Council. An Assessment of Atlantic Bluefin Tuna. Washington DC National Academy Press, 1994.

Due to ever lower stocks of bluefin tuna in the Atlantic and Mediterranean, a common practice has emerged of catching juvenile fish and keeping them in offshore tuna ranches. Such facilities are operated by Spanish, French, Italian, Greek, Turkish, Cypriot, Croatian, Egyptian, Libyan, Tunisian, Algerian, Moroccan, and Maltese fishers. Because the fish are caught before they reach reproductive age, and because they are then kept isolated until they are killed, such ‘ranching’ exacerbates the destruction of tuna populations.

“Japanese scientists at the National Research Institute of Aquaculture, Fisheries Research Agency have reported that they successfully completed an artificial cultivation cycle for unagi, or eel — a world first. Unagi is a traditional delicacy in Japan, and can commonly be found in baked form at sushi restaurants. The fish has long been caught either matured, or still young and then fattened on farms. Sadly, as a result, natural stocks of unagi have plummeted in recent years. However, the research news indicates a future method to completely farm breed the tasty creature in mass quantity. Good news for sushi lovers, Japanese businesses, and wild eel alike.”

DURING May and June, when the mighty bluefin tuna returns to the Mediterranean to spawn, fishermen arrive from all over the world to catch it. In days gone by, the fish were netted and killed on the spot. Now, in high-tech operations involving divers and video cameras, they are transferred from the nets into “farms”—arrays of cages anchored to the sea floor from Spain to Malta, to be fattened up. Then, come October, they are sold to Japanese boats, killed, frozen and shipped to Japan.

It is a lucrative arrangement. Anthony Grupetta, the director general of agriculture and fisheries regulation in Malta, says that in those few months most farmers can increase the weight of a wild-caught bluefin by 27-30%. (He claims the Maltese farms do better than this, but does not say exactly how much better.) The cages do not cost much, and the fish fed to a tuna are worth a lot less than the added kilos of tuna-meat that result. What is more, Japanese buyers prefer fish raised this way. They say the quality of the meat from a bluefin killed straight after being caught is less tasty, as the fish has been stressed.

Charlie Azzopardi, the managing director of Azzopardi Fisheries, which runs two of Malta’s seven farms, brought the idea of raising caged bluefin to Malta ten years ago, after seeing it done in Spain and Australia. According to Mr Azzopardi the bluefin industry now generates about 1.5% of Malta’s GDP. Japanese freezer boats take 95% of his production. The other 5% is sold fresh, to order, at all times of year. It can be a precarious business, though. A collapse in demand meant the price of bluefin fell by 40% last year and Mr Azzopardi chose to keep his fish on the farm until prices improved. On the supply side, fishermen complain that the size of the bluefin they are catching has plummeted in recent years. That reduction in individual size could be the result of a reduction in the tuna population that is causing fewer fish to reach maturity.

Mr Azzopardi says that despite the warnings from scientists, he does not believe the numbers of wild fish are falling. A number of green groups disagree, and believe that the quota allowed for fishing in these parts is far too high. One activist group, Greenpeace, has attempted to take matters into its own hands and has made several attacks on legal tuna-fishing operations over the past few weeks.

Japanese call bluefin tuna “the king of fish”. They eat about 40,000 tonnes of it a year—80% of the global catch. Demand is also growing rapidly elsewhere. Yet Pacific bluefin stocks are down by 97% from their peak in the early 1960s, according to a recent report from the International Scientific Committee, an intergovernmental panel of experts. (Japan disputes its findings.) In some places, fishing is three times the sustainable level, the committee says.

Japan did agree to halve its catch of juvenile bluefin (fish too young to reproduce) in the northern Pacific last year. But it has resisted more stringent measures, including the complete ban on bluefin fishing advocated by America, among other countries. The Japanese government says that would not be warranted unless stocks drop for three years in a row—a hurdle that most conservationists consider too high.